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United States Patent |
6,109,393
|
Toyota
,   et al.
|
August 29, 2000
|
Gear type of manual transmission for automotive vehicle
Abstract
An output reduction gear type of manual transmission having a reduction
gear chamber formed by partitions disposed on opposite sides of a
reduction gear unit, an oil inflow structure comprising an oil inflow
passage formed at a lower end of the reduction gear unit and tapered
roller bearings supporting an output shaft and a counter shaft which are
coupled by the reduction gear unit, an oil outflow structure comprising an
oil tray which collects oil splashed by the counter shaft and the
reduction gear unit and an oil outflow passage formed at an upper part of
the reduction gear unit.
Inventors:
|
Toyota; Hideo (Hiroshima, JP);
Yoshimoto; Naoaki (Hiroshima, JP)
|
Assignee:
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Mazda Motor Corporation (Hiroshima, JP)
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Appl. No.:
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941205 |
Filed:
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September 30, 1997 |
Foreign Application Priority Data
Current U.S. Class: |
184/6.12; 74/606R; 184/11.2; 184/13.1 |
Intern'l Class: |
F16H 057/00 |
Field of Search: |
184/13.1,11.2,6.12
74/606 R,473.1
|
References Cited
U.S. Patent Documents
3195682 | Jul., 1965 | Reneerkens | 184/6.
|
3618711 | Nov., 1971 | Vollmer | 184/6.
|
4222283 | Sep., 1980 | Nagy | 74/467.
|
4231266 | Nov., 1980 | Nishikawa et al. | 74/467.
|
4329887 | May., 1982 | Kawamoto | 74/467.
|
4359909 | Nov., 1982 | Sogo | 74/467.
|
5052238 | Oct., 1991 | Sewell | 74/473.
|
5092196 | Mar., 1992 | Kameda et al. | 74/606.
|
5325739 | Jul., 1994 | Toyota et al. | 74/606.
|
5946971 | Sep., 1999 | Toyota et al. | 74/606.
|
Foreign Patent Documents |
2-22452 | Feb., 1990 | JP.
| |
2-38736 | Feb., 1990 | JP.
| |
2-931 51 | Apr., 1990 | JP.
| |
Other References
Marks' Standard Handbook of Mechnical Engineers, pp. 8-132-8-133, 1978.
|
Primary Examiner: Bucci; David A.
Assistant Examiner: Joyce; William C
Attorney, Agent or Firm: Nixon Peabody LLP, Studebaker; Donald R.
Claims
What is claimed is:
1. A manual transmission for an automotive vehicle, comprising:
an input shaft;
an output shaft coaxially aligned with said input shaft in a straight line;
a counter shaft disposed below in parallel with said input shaft and said
output shaft and always operationally coupled to said output shaft by a
reduction gear unit;
a plurality of gear units including forward gear units having different
gear ratios and a reverse gear unit;
gear shift means for selectively bringing said gear units into operation to
couple said input shaft and said counter shaft to transmit a rotation of
said input shaft to said output shaft through said counter shaft so as
thereby to provide the transmission with desired gear ratios;
a transmission case enclosing all of said shafts and said gear units and
containing oil in a bottom section thereof:
partition means for forming a gear chamber in an output side section of
said transmission case which encloses and isolates said reduction gear
unit from said gear units, said partition means comprising a front and a
rear partition which cooperate with interior walls of said transmission
case;
oil supply means for supplying oil contained in said bottom section of said
transmission case into said gear chamber; and
oil return means for causing splashes of oil spattered by said reduction
gear unit to flow out of said gear chamber toward said bottom section of
said transmission case;
wherein said oil return means comprises:
an oil outflow passage formed in an upper part of said partition means
above said reduction gear unit through which the inside and the outside of
said gear chamber are communicated with each other; and
an oil tray is formed integrally with said transmission case and disposed
off a vertical plane enclosing center lines of rotation of said output
shaft and said counter shaft to be adjacent to said oil outflow passage so
as to receive splashes of oil spattered by said reduction gear unit.
2. A manual transmission as defined in claim 1, wherein said oil tray is
positioned off said vertical plane on a side remote from a side wall of
said transmission case to which said counter shaft directs splashes of oil
directly.
3. A manual transmission for an automotive vehicle as defined in claim 1,
further comprising:
a reverse idler shaft provided with a reverse idler gear which is capable
of being brought into mesh with a reverse gear unit;
wherein said oil flow passage includes divisional oil flow passages formed
in said reverse idler shaft and said counter shaft, respectively, and
connected to each other so as to supply oil in said bottom section of said
transmission case to moving parts to be lubricated on input side sections
of said input shaft, said counter shaft and said reverse idler shaft
through said oil flow passage.
4. A manual transmission as defined in claim 3, wherein said oil supply
means comprises at least one tapered roller bearing for supporting said
output shaft and said counter shaft on both sides of said reduction gear
unit, each said tapered roller bearing being supported by at least one of
said front and rear partitions.
5. A manual transmission as defined in claim 3, wherein said oil supply
means comprises an oil inflow passage formed in a lower part of said
partition means through which the inside and the outside of said gear
chamber are communicated with each other.
6. A manual transmission as defined in claim 3, wherein said oil return
means comprises an oil outflow passage formed in an upper part of said
partition means above said reduction gear unit through which the inside
and the outside of said gear chamber are communicated with each other.
7. A manual transmission as defined in claim 6, wherein said oil return
means further comprises an oil tray disposed adjacent to said oil outflow
passage to receive oil splashed by said reduction gear unit.
8. A manual transmission as defined in claim 7, wherein said oil tray is
formed integrally with said transmission case.
9. A manual transmission as defined in claim 8, wherein said oil tray is
positioned off a vertical plane enclosing center lines of rotation of said
output shaft and said counter shaft.
10. A manual transmission as defined in claim 9, wherein said oil tray is
positioned off said vertical plane on a side remote from a side wall of
said transmission case to which said reduction gear directs splashes of
oil directly.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a gear type of manual transmission for an
automotive vehicle, and, more particularly, to a gear type of manual
transmission having an improved lubrication system for an automotive
vehicle.
2. Description of Related Art
A gear type of manual transmissions connected, for example, to an engine
which is installed in an engine compartment of an automotive vehicle with
its output shaft directed in the longitudinal direction of the vehicle
generally include four shafts, namely input and output shafts arranged in
coaxial alignment with each other, a counter shaft arranged in parallel
with those input and output shafts, and a reverse idler shaft. Counter or
cluster gears of a plurality of gear units are disposed on the counter
shaft, and others are disposed on either the input shaft or the output
shaft, or the reverse idler shaft.
The manual transmission generally transmits input torque to the counter
shaft through a unit of an input gear and a counter reduction gear at a
specified reduction ratio and then to the output shaft through selected
one of various speed gear units. This manual transmission is called an
"Input Reduction Gear Type" because speed reduction is made between the
input shaft and the counter shaft. The input reduction gear type of manual
transmission has an input gear and a reduction gear fixed to the input
shaft and the counter shaft, respectively.
Manual transmissions, which are called an "Output Reduction Gear Type,"
have a reduction gear unit comprising an output reduction gear and a
counter reduction gear fixedly disposed on the output shaft and the
counter shaft, respectively, to reduce output torque. Such an output
reduction gear type of manual transmission is known from, for example,
Japanese Unexamined Patent Publication No. 2-93151. In this type of manual
transmission, input torque is transmitted to the counter shaft without
being multiplied, and torque applied to each of the counter gears except
the counter reduction gear is low consequently. While the transmission has
the advantage that the counter gears are made small in diameter and thin,
which is always desirable for the transmission to be small in size,
nevertheless, various constraints are imposed on the counter reduction
gear. Specifically, since torque is reduced by the reduction gear unit
before transmitted to the output shaft, the output reduction gear is
required to have strength and rigidity higher than the input reduction
gear of the input reduction gear type of manual transmission, and
consequently required to have a large face width. Due to the output
reduction gear which has a large face width and to which large torque is
applied, parts of the output shaft and the counter shaft on which the
reduction gears are disposed and firmly borne or supported by strong
bearing structures. As taught in, for example, Japanese Unexamined Utility
Patent Publications Nos. 2-22452 and 2-38736, in order to meet the demand,
it is known to use tapered roller bearings, which are capable to withstand
both high radial and thrust loads, to support the output shaft and/or the
counter shaft on both sides of the reduction gear. Regarding tapered
roller bearings used in the transmission, it is known in the art that
lubricating oil is easily drawn in a direction of a diameter change from
small to large of an inner race of the tapered roller bearing due to a
centrifugal force generated by revolutions of the shaft fitted in the
inner race.
Further, considering the rotational speed of the counter shaft of the input
reduction gear type of conventional manual transmission, it depends upon
the gear ratio of a reduction gear unit disposed between the input and
counter shafts, and hence lower than the speed of rotation of the input
shaft in spite of gears. As against, the rotational speed of the counter
shaft of the output reduction gear type of manual transmission depends
upon the gear ratio of a selected gear. Accordingly, it is increased
higher than that of the input shaft when the selected gear is somewhat
higher. In other words, if both types of manual transmissions have
reduction gear units of a same gear ratio, the rotational speed of the
output reduction gear type of manual transmission is significantly higher
than that of the input reduction gear type of manual transmission when
specific higher gears are selected. In such a case, the counter reduction
gear turns at a significantly high rotational speed.
While the counter shaft rotates at an increased rotational speed, a bearing
for any racing gear (which refers to a gear rotating relatively to the
shaft on which it is disposed) is put under extremely rigorous lubrication
conditions. Especially, a racing gear of a reverse gear unit rotates in an
opposite or counter direction to the direction of rotation of the counter
shaft by means of the reverse idler gear, the relative speed between the
counter shaft and the racing gear becomes extremely higher. Regarding a
reverse and a first gear unit which have large reduction ratios, in the
case that a smaller gear of the reverse gear unit or the first gear unit
is disposed for relative rotation on the input shaft, the relative speed
of the small gear with respect to the input shaft is extremely high,
putting the bearing of the racing gear, in particular, under extremely
rigorous lubrication conditions.
In the gear type of manual transmission, the utilization is made of counter
racing gears to splash and supply oil in an oil sump of the transmission
housing to mating teeth of gears and bearings for racing gears and their
associated moving parts for lubrication. The oil splashes mostly hit
against an interior wall of the transmission case and flows down along the
wall. During flowing down, the oil looses heat and is cooled to some
degree before supplied to those moving parts.
It is necessary to consider effects of stir resistance caused due to
rotations of the counter shaft and counter gears to temperature of
lubricating oil. In order to decrease the stir resistance to control an
increase in oil temperature, it is desirable to reduce the amount of
lubricating oil as small as possible within the limits. For the output
reduction gear type of manual transmission, in particular, there is a
strong demand for decreasing the amount of lubricating oil because, while
a higher gear is provided, the rotational speed of the counter gear is
higher as compared with that of the input reduction gear type of manual
transmission. However, it is hard for the conventional manual
transmissions to overcome these somewhat conflicting demands that govern
decreasing the amount of lubricating oil and reliable lubrication of
moving parts of the transmission.
SUMMARY OF THE INVENTION
It is accordingly a primary object of the invention to provide a gear type
of manual transmission which performs reliable and efficient supply of
lubricating oil to moving parts.
The foregoing object of the invention is accomplished by providing what is
called an output reduction gear type of manual transmission which has a
reduction gear unit always operationally coupling a counter shaft to an
output shaft disposed in parallel with the counter shaft to transmit a
rotation of the counter shaft to the output shaft and a plurality of gear
units having different gear ratios which are brought into operation to
couple the input shaft to the counter shaft to transmit a rotation of the
input shaft to the output shaft through the counter shaft so as thereby to
provide desired gear ratios of the transmission gear. The transmission at
an output side is provided with a partition means, such as including a
front and a rear partition, to form a gear chamber in a transmission case
so as to enclose and isolates the reduction gear from the transmission
gear units, an oil supply means for supplying oil reserved in a bottom
reservoir of the transmission case into the gear chamber, and an oil
return means for causing oil splashed up by the reduction gear to flow out
of the gear chamber toward the bottom reservoir section.
Oil supply means comprises at least one of tapered roller bearings held by
the partitions for supporting the output shaft and the counter shaft on
both sides of the reduction gear and may further comprise an oil inflow
passage formed in a lower part of the partition through which the inside
and the outside of the gear chamber are communicated with each other. The
oil return means comprises an oil outflow passage formed in an upper part
of the partition above the reduction gear through which the inside and the
outside of the gear chamber are communicated with each other and further
may comprise an oil tray, preferably formed integrally with the
transmission case, which is disposed adjacent to the oil outflow passage
to receive oil splashed by the reduction gear. The oil tray is positioned
off a vertical plane enclosing center lines of rotation of the output
shaft and the counter shaft. More specifically, the oil tray is preferably
positioned off said vertical plane on a side remote from a side wall of
the transmission case against which the counter shaft and the reduction
gear splash oil directly.
The output reduction gear type of transmission of the invention may have a
input side lubrication system comprising divisional oil flow passages
which are formed in a reverse idler shaft, the input shaft and the counter
shaft, respectively, and connected in series in this order so as to supply
oil in the bottom reservoir of the transmission case to moving parts to be
lubricated which are disposed on input side sections of those shafts
therethrough.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects of the present invention will be understood
from the following description of a specific embodiment thereof when
considering in conjunction with the accompanying drawings, in which:
FIG. 1 is a cross-sectional view schematically showing an overall
construction of a gear type of manual transmission in accordance with an
embodiment of the invention;
FIG. 2 is an enlarged cross-sectional view showing essential part of an
input side of a transmission gear assembly of the transmission;
FIG. 3 is an end view of a clutch housing as viewed in a direction A--A in
FIG. 2;
FIG. 4 is an end view of a front cover as viewed in a direction B--B in
FIG. 2;
FIG. 5 is an explanatory view, partly in sectional, showing a reverse idler
shaft fitted to a transmission case;
FIG. 6 is an explanatory view, partly in sectional, showing a reverse idler
gear disposed on the reverse idler shaft;
FIG. 7 is an explanatory view showing the installed height of the reverse
idler shaft;
FIG. 8 is an enlarged cross-sectional view showing essential part of an
output side of the transmission gear assembly of the gear type of
transmission shown in FIG. 1;
FIG. 9 is an end view of a transmission housing as viewed in a direction
C--C in FIG. 8; and
FIG. 10 is an end view of an extension housing as viewed in a direction
D--D in FIG. 8.
DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT
Referring to the drawings in detail, particularly to FIG. 1, a gear type of
manual transmission (which is hereafter referred to as a transmission for
simplicity) TM in accordance with an embodiment of the invention is shown.
In this embodiment, the transmission TM, which is connected to an engine
(not shown) arranged with its crankshaft directed in a longitudinal
direction of what is called a front engine-rear drive type of automotive
vehicle, has five forward speed gear units 1G-5G and one reverse gear 6G
and is designed and adapted to directly interconnect an input and an
output shaft by means of, for example, the fourth speed gear unit.
The transmission TM has an input and an output shaft Si and So arranged
coaxially in a straight line and a counter shaft Sc disposed below and in
parallel with these input and output shafts Si and So in a transmission
housing 5. The transmission TM further has a plurality of gear units 1G-6G
having different gear ratios, Each gear unit, one gear of which is
disposed on either the input shaft Si or the output shaft So and the other
is disposed on the counter shaft Sc, are brought into mesh with each other
when the transmission TM is shifted to the gear. As will be described in
detail later, the transmission is of the output reduction gear type which
has a reduction gear unit 4G consisting of an output reduction gear 4Go
fixed to the output shaft So and a counter or counter reduction gear 4Gc
fixed to the counter gear Sc. The reduction gear unit 4G is preferably
positioned at one end of the counter shaft Sc closer to an output end of
the transmission TM.
Input shaft Si at one of its ends (on the left side as viewed in FIG. 1) is
connected to an output shaft (not shown) of the engine by means of an
engine clutch 1. On the other hand, the input shaft Si at another end or
output end (on the right side as viewed in FIG. 1) is joined together to
one of its ends, namely an input end, of the output shaft So. The output
shaft So at another or output end is connected to a propeller shaft (not
shown) through a sleeve shaft 3. The transmission case is comprised of a
clutch housing, a transmission housing 5 and rear extension housing 6
arranged in the longitudinal direction in order from the engine side and
connected to one another. The transmission case is formed with partitions
11-13 extending radially from the interior walls of the housings 4-6 by
which bearings are held to support the shafts Si, So and Sc in the
transmission case. In this instance, the partition 11 formed between the
clutch housing 4 and the transmission housing 5 is closed by a front cover
15. The extension housing 6 is provided with a shift lever gate chamber 19
in which a shift lever 2 and three shift rods 17 (only one of which
appears in FIG. 1) are partly accommodated and which is covered at a top
by a cover 16.
Gear assembly arranges, in order from the input side to the output side the
fifth speed gear unit 5G, the reverse gear unit 6G, the first speed gear
unit 1G, the second speed gear unit 2G, the third speed gear unit 3G and
the reduction gear unit 4G, and is divided into, for example, three groups
as a 5-R group (the fifth and reverse gear units 5G and 6G), a 1-2 group
(the first and second gear units 1G and 2G) and a 3-4 group (third and
fourth gear units 3G and 4G). The reverse gear unit 6G, the second speed
gear unit 2G and the reduction gear unit 4G are disposed on the output
sides of the respective gear units, respectively, as output gears of the
gear units. Among the counter gears, a third and a fourth counter gear 3Gc
and 4Gc are fixedly installed to the counter shaft Sc, and the remaining
counter gears 1Gc, 2Gc, 5Gc and 6Gc are installed as racing gears on the
counter shaft Sc.
As shown in FIGS. 5-7, the reverse gear unit 6G includes a reverse idler
gear Gr fixedly installed to a reverse idler shaft Sr which operationally
couples the fixed reverse gear 6Gi and the counter reverse idler gear 6Gc
and drives the output reverse gear 6Gi in a direction opposite to the
direction of rotation of output gears of the forward speed gear units
1G-5G. The reverse idler shaft Sr, which is supported by and between the
partition 11 and a fitting mount 8 fastened to the transmission housing 5
by a bolt 9, has a lengthwise or axial flow passage of oil Lr extending to
the bearing holding the reverse idler gear Gr. As seen clearly in FIG. 7,
the reverse idler shaft Sr is positioned to locate the center axis of
rotation Cr at a vertical height slightly lower than the center axis of
rotation Ci of the input shaft Si but somewhat higher than the center axis
of rotation Cc of the counter shaft Sc.
Referring back to FIG. 1, the reduction gear unit 4G consists of the output
and counter gears 4Go and 4Gc installed as fixed gears on the output shaft
So and the counter shaft Sc, respectively. The output reduction gear 4Go
is coupled to the input shaft Si by a needle bearing secured to the output
shaft So so as to rotate relatively to the input shaft Si. That is, the
reduction gear unit 4G forms a reduction gear unit to impart a reduced
rotation to the output shaft So from the counter shaft Sc. This structure
of the reduction gear unit with the output reduction gear 4Go and the
counter reduction gear 4Gc operationally integral with the output shaft So
and the counter shaft Sc, respectively, forms the transmission TM as an
output reduction gear type. During engine idle or while the transmission
TM is left neutral, the counter shaft Sc does not race.
Since the transmission TM constructed in the output reduction gear type
imparts the engine torque to the counter shaft Sc from the input shaft Si
with no torque multiplication, loads applied to the component gears except
the reduction gear unit 4G is low, which is always desirable for the
respective gear units to be made thin and small in size. However, because
the reduction gear unit 4G at a position closest to the output end of the
gear assembly reduces a rotation of the counter shaft Sc with torque
multiplication, the output reduction gear 4Go and the counter reduction
gear 4Gc are as a necessity strength and rigid more as compared with those
of the conventional input reduction gear type of transmission, which leads
to a large face width.
Each gear group is accompanied by a synchronizing mechanism, which is
otherwise called a synchro-mesh mechanism, Ya, Yb, Yc to mesh one gear of
a gear unit with another quietly and without damage. The synchronizing
mechanisms Ya and Yc for the 1-2 gear group and the 5-R gear group,
respectively, of which the counter gears are idling, are installed on the
counter shaft Sc, and the synchronizing mechanism Yb for the 3-4 gear
group, of which the input gears are idling, is installed on the input
shaft Si. Such synchronizing mechanisms are well known in construction and
operation to those skilled in the art, so that a more detailed description
is not necessary.
When the shift lever 2 is operated to bring any gear unit other than the
reduction gear unit ready, the racing gear of a corresponding gear unit is
coupled in motion to the shaft on which the racing gear is installed and
brought into mesh with the counter gear of the gear unit, driving the
counter shaft Sc. When the counter shaft Sc is turning, a rotation is
reduced by the reduction gear unit 4G and imparted to the output shaft So
with torque multiplication through the reduction gear unit 4G. However,
when ready for the reduction gear, the input and output shafts Si and So
are directly coupled in motion.
Different from the conventional input reduction gear type of transmission,
the output reduction gear type of transmission provides different
rotational speeds of the counter shaft Sc for different speed gears.
Specifically, the counter shaft Sc turns at speeds higher than the input
shaft Si when it is in specified higher speed gears. When the counter
shaft Sc turns faster than the input shaft Sc, the bearing of a racing
gear of any gear unit is put under extremely rigorous lubrication
conditions while the racing gear is racing. In particular, when the
counter shaft Sc is turning, the counter reverse idler gear 6Gc also
turns, but in an opposite or counter direction by means of the reverse
idler gear Gr. As a result, the counter idler gear 6Gc turns at a
significantly high relative rotational speed with respect to the counter
shaft Sc. In the case that the first speed gear unit 1G or the reverse
gear unit 6G, which has a relatively high reduction ratio, has a small
gear as a racing gear, the rotational speed of the racing gear relative to
the shaft on which the racing gear is installed is significantly high when
the transmission is in higher speed gears. The bearing holding such a
racing gear is put under especially rigorous lubrication conditions.
If all of the synchronizing mechanisms Ya-Yc are installed on the input
shaft Si, the gears on the input shaft Si, which are all racing, in
particular the small gears of the first speed gear unit 1G and the reverse
gear unit 6G, get significantly high rotational speeds relative to the
input shaft Si when the transmission is in higher speed gears. As a
result, the counter shaft Sc is in a condition to turn at an increased
rotational speed, there are apprehensions of seizing or burning in the
bearing for the racing gear. In particular, the bearing for the counter
reverse idler gear 6Gc turning in an opposite or counter direction
relative to the counter shaft Sc is conspicuous for showing a high
tendency to seize.
From the above technical background, the transmission TM of the invention
has an arrangement of the synchronizing mechanisms Ya and Yc for the 1-2
gear group and the 5-R gear group, respectively, installed on the counter
shaft Sc and their related small gears 1Gi and 6Gi of the first speed gear
unit 1G and the reverse gear unit 6G, respectively, fixedly installed on
the input shaft Si. Accordingly, the small gears 1Gi and 6Gi turn at the
same rotational speed as the input shaft Si in spite of selected speed
gears. The counter large gears 1Gc and 6Gc of the first speed gear unit 1G
and the reverse gear unit 6G, which are installed for rotation on the
counter shaft, turn relatively to the counter shaft Sc at a relative
rotational speed lower than the rotational speed of the smaller input
shaft gears 1Gi and 6Gi, the transmission TM of the invention encounters
no large difference in relative rotational speed which occurs between the
racing gear of the first speed unit 1G or the racing gear of the reverse
gear unit 6G and the input shaft Si in an output reduction gear type of
transmission with the synchronizing mechanisms Ya and Yc arranged on the
input shaft Si.
Output reduction gear type of transmission described above provides a
significantly high rotational speed of the counter shaft Sc in higher
speed gears, and accordingly, the bearings for the racing gears 1Gc, 2Gc,
5Gc and 6Gc, in particular the counter small gear 5Gc, on the counter
shaft Sc are put under especially rigorous lubrication conditions. It is
also important how to reliably supply lubricating oil to the bearing for
the reverse idler gear Gr placed between the fixed reverse gear 6Gi and
racing reverse idler gear 6Gc of the reverse gear unit 6G.
Similarly to the conventional gear type of transmission, the output
reduction gear type of transmission TM of the invention contains
lubricating oil in the transmission case, in particular in the
transmission housing 5 and extension housing 6 at a specified level as
shown by a double-dotted straight line in FIG. 1. It is noted that the
transmission TM is installed with a small inclination to the horizontal
plane. Counter gears on the counter shaft Sc positioned closer to the
bottom of the transmission case are used to splash and supply the oil to
mating teeth of various gear units 1G-6G and the bearings for the racing
gears 1Gi-3Gi, 5Gi and 6Gi, and other moving parts to be lubricated. The
oil splashes mostly hit against an interior wall of the transmission case
and flow down along the interior wall of the transmission case. During
flowing down, the oil looses heat and is cooled to some degree before
supplied to those moving parts.
In order to reduce stir resistance of the oil caused due to a rotation of
the counter gears and the counter shaft Sc on which a rise in oil
temperature depends, it is desired to decrease the amount of oil staying
in the transmission case to a level as low as permissibly. There is an
especially strong demand for decreasing the amount of oil in the
transmission case on the output reduction gear type of transmission of
which the counter shaft Sc turns at a speed significantly higher in higher
speed gears as compared with the input reduction gear type of
transmission. For that reason, the transmission TM of the invention is
incorporated with a contrived flow passage of oil for the gear assembly at
the input side which achieves both decrease in the amount of oil to be
filled in the transmission case and reliable lubrication of the moving
parts. The flow passage of oil comprises three parts of flow passages of
oil formed in the reverse idler shaft Sr, the input shaft Si and the
counter shaft Sc, respectively, which are connected in series in this
order.
As shown in detail in FIGS. 2-4, in the interior of the transmission TM,
there is provided an oil tray 20, laterally off the upper front of the
fixed gear 5Gi of the fifth speed gear unit 5G, the foremost gear unit of
the gear assembly and secured to the interior wall of the clutch housing
4, which collects oil splashes or drops splashed up by the counter shaft
Sc and the gears thereon, and a connecting flow passage of oil 21 leading
to an oil chamber 22 defined by the partition 11, bearings Bil and Bcl
fitted to the partition 11 and the front cover 15. As shown in FIG. 4, the
oil chamber 22 comprises an oil catcher 22a corresponding in position to
the connecting flow passage of oil 21, an oil reservoir 22b corresponding
in position to the axial flow passage of oil Lr of the reverse idler shaft
Sr, a bearing support bore 22c in which the ball bearing Bil is fitted, a
bearing support bore 22e in which the cylindrical roller bearing Bcl is
fitted, and an oil reservoir 22d between the bearing support bores 22c and
22e, all of which are formed in the front cover 15 and form an oil
gallery. A route of oil supply is defined by the oil gallery. Another
front cover formed with a different pattern of oil gallery may be employed
to provide a different route of oil supply, As shown in FIG. 5, an oil
sealing ring or gasket 15s is incorporated between the input shaft Si and
opening of the front cover 15. Forming an oil chamber with such an oil
gallery guarantees a high degree of freedom of laying out of flow passages
of oil. The counter shaft Sc at its input end is formed with a short axial
flow passage of oil Lc. An annular space between the inlet end of the
axial flow passage of oil Lc and the outer race of the cylindrical roller
bearing Bcl supporting the end of the counter shaft Sc is covered by an
end cover 23h.
With the fixed reduction gear type of transmission TM with the flow passage
of oil which supplies lubricating oil to moving parts through the reverse
idler shaft Sr, the input shaft Si and the counter shaft Sc in this order,
the bearing of the reverse idler gear Gr is reliably supplied with oil.
Further, since these the reverse idler shaft Sr, the input shaft Si and
the counter shaft Sc are also arranged in the order of difficulty of oil
supply, moving parts on each shaft are lubricated reliably and efficiently
to be prevented from seizing.
In order to reduce the amount of lubricating oil necessary to stay in the
transmission case and lubricate the gear assembly at the output side and
other moving parts, such as bearings, reliably and efficiently, the
transmission TM imposes a burden as an oil pump on the reduction gear
unit, i.e. the reduction gear unit 4G. Specifically, as was previously
described, while the gears other than the counter gear 4Gc of the
reduction gear unit 4G as a counter reduction gear are made small, the
counter gear 4Gc of the reduction gear unit 4G has a large face width and
is made strong and rigid due to the necessity of reducing a rotation of
the counter shaft Sc and transmitting it to the output shaft So with
torque multiplication. Further, the counter shaft Sc turns at a speed
significantly higher in higher speed gears as compared with the input
reduction gear type of transmission, the forth speed gear unit 4G turns at
a considerably high speed. For those reasons, parts of each of the counter
shaft Sc and the output shaft So must be rigidly supported on opposite
sides of the gears 4Gc and 4Go of the reduction gear unit 4G.
As shown in FIG. 8, the transmission TM is provided in the interior thereof
with a reduction gear chamber 25 formed by the partitions 12 and 13 on
opposite sides of the reduction gear unit 4G, respectively, and the
transmission case. The partitions 12 and 13 support bearings Bo1 and Bo2
disposed on the output shaft So on opposite sides of the output forth
speed gear 4Go and bearings Bc2 and Bc3 disposed on the counter shaft Sc
on opposite sides of the counter forth speed gear 4Gc. Lubricating oil is
easily drawn into the reduction gear chamber 25 due to a certain degree of
negative pressure produced due to a high speed rotation of the counter
shaft Sc. In other words, the reduction gear unit 4G works as an oil pump.
In this embodiment, the utilization is made of tapered roller bearings,
which withstand both high radial load and high thrust load, for the
bearings Bo1, Bo2, Bc2 and Bc3, providing a strong and rigid support
structure of the output shaft So and the counter shaft Sc. The utilization
of tapered roller bearings creates a fluid flow path directed from the
smaller diameter of the inner race toward the larger diameter thereof due
to the effect of centrifugal force generated by revolutions of the inner
race and rollers of the bearing to which the shaft is fitted. Accordingly,
lubricating oil is easily drawn into the reduction gear chamber 25 through
the tapered roller bearings along the fluid flow paths shown by solid
arrows in FIG. 8, and the supplied amount of lubricating oil depends upon
the rotational speed of the output shaft So and/or the counter shaft Sc.
Output reduction gear, i.e. the output reduction gear 4Go, is integrally
formed, or otherwise provided, with fins 50 on the front surface to scoop
and direct lubricating oil into a radial flow passage of oil 49 for
lubrication of a needle bearing Bi2 fitted to the extreme end of the input
shaft Si. The transmission TM collects oil in a bottom reservoir 10 which
lubricates the counter gear assembly including 5Gc, 6Gc and 1Gc-3Gc
arranged in this order from the input side are lubricated. Further, the
partition 12 at its lower end is cut off to provide an oil inflow passage
5a between the bottom reservoir 10 and a bottom portion of the reduction
gear chamber 25, through which the lubricating oil in the reservoir is
easily drawn into the reduction gear chamber 25.
Referring to FIGS. 9 and 10, the transmission housing 5 at its rear end is
provided, or may be formed integrally, with an oil tray 26 disposed above
the reduction gear unit 4G so as to collect oil splashes or drops splashed
by the reduction gear unit 4G therein. The oil tray 26 is positioned
laterally off a vertical plane Loc in which axial center lines Co and Cc
of the output shaft So and the counter shaft Sc lie, so as to cause no
interference with parts of the partitions 12 and 13 where the shift rods
17 are supported. It is preferred that the oil tray 26 is positioned off
the vertical plane Loc on the side remote from a housing wall to which the
counter shaft Sc directs splashes of oil directly. The splashes of oil are
mostly directed to the wall of the transmission case first and then flow
down along the interior wall of the transmission case. The oil collected
in the oil tray 26 flows out of the reduction gear chamber 25 through a
return flow passage of oil 28 formed in the partition 12. The oil flowing
out of the reduction gear chamber 25 is partly directed into the shift
lever gate chamber 19 in which the shift lever 2 and the shift rods 17
(only one of which appears in FIG. 1) are partly accommodated through an
oil outflow passage 27 formed in the partition 13 and partly returned into
the bottom reservoir 10 in the transmission housing 5 through the return
flow passage of oil 28. The lubricating oil supplied into the shift lever
gate chamber 19 lubricates the sleeve shaft 3. In the case that the oil
tray 26 is formed as integral parts of the transmission housing 5 and the
extension housing 6, oil received by the oil tray 26 dissipates heat
efficiently through the transmission case. The off set position of the oil
tray 26 makes it possible to cool the splashes of oil during flowing down
to the oil tray 26 along the interior wall of the transmission case due to
dissipation of heat through the wall and to collect the splashes of oil
efficiently. Further, the off set position of the oil tray 26 allows the
transmission case to have a decreased overall height.
As described above, with the construction of the output reduction gear type
of transmission TM of the invention that the partitions 12 and 13 disposed
on opposite sides, i.e. the input side and the output side, of the
reduction gear unit 4G, respectively, are provided with means comprising
the tapered roller bearings Bo1, Bo2, Bc2 and Bc3 and the oil inflow
passage 5a for supplying oil into the reduction gear chamber 25 defined
between the partitions 12 and 13 and means comprising the oil tray 26 and
the return flow passage of oil 28 for allowing oil splashed by the counter
reduction gear 4Gc to flow out of the reduction gear chamber 25, it is
made possible to impose a burden as an oil pump on the reduction gear unit
4G which comprises gears having large face widths and rotates at a high
speed. In addition, even when a reduced amount of oil is used, moving
parts necessary to be lubricated are supplied with oil reliably and
efficiently. In other words, while the moving parts are reliably supplied
with oil, it is realized to reduce stir resistance of the oil caused due
to rotations of the counter shaft Sc and the counter gears 1Gc-6Gc, which
leads to suppression of an increase in oil temperature and control of
aggravation of the mechanical efficiency of power transmission as well.
For the input side part of the gear assembly comprising the various speed
gear units 1G-6G, a series flow passage of oil is incorporated, which
comprises three parts of flow passages of oil formed in the reverse idler
shaft Sr, the input shaft Si and the counter shaft Sc, respectively and
connected in this order. This flow passage of oil makes it possible that,
even while a somewhat reduced amount of oil is utilized, oil is reliably
and efficiently supplied to the necessary moving parts related to those
shafts. On the other hand, for the output side part of the gear assembly,
the utilization is made of the reduction gear unit 4G enclosed in the
reduction gear chamber 25 both for a reduction gear unit and for an oil
pump. This makes it possible that, even while a somewhat reduced amount of
oil is utilized, oil is reliably and efficiently supplied to the necessary
moving parts. Accordingly, in the output reduction gear type of
transmission of the invention, while the gear assembly is properly
lubricated at an input and an output side, the whole gear assembly is
efficiently supplied with lubricating oil. In addition, it is realized to
reduce stir resistance of the oil caused due to rotations of the counter
shaft and the counter gears with the result of suppression of an increase
in oil temperature and control of aggravation of the mechanical efficiency
of power transmission.
As described in detail above, with the output reduction gear type of
transmission TM of the invention, the reduction gear, whose component
gears have large face widths and turn at a rotational speed higher as
compared with the conventional input reduction gear type of transmissions,
and the reduction gear chamber having an oil supply means and an oil
return means cooperate to work as an oil pump for lubrication. This
lubrication system realizes proper and efficient lubrication of the gear
assembly and its associated moving parts with an decreased amount of oil.
In other words, it is realized to reduce stir resistance of the oil caused
due to rotations of the counter shaft and the counter gears with the
result of suppression of an increase in oil temperature and control of
aggravation of the mechanical efficiency of power transmission.
The utilization of tapered roller bearings for supporting the counter shaft
and/or the output shaft creates a fluid flow path directed from the
smaller diameter of the inner race toward the larger diameter thereof due
to the effect of centrifugal force generated by revolutions of the inner
race and rollers of the bearing to which the shaft is fitted, so that
lubricating oil is easily drawn into the reduction gear chamber through
the tapered roller bearings along the fluid flow paths correspondingly in
amount to the rotational speed of the output shaft or the counter shaft.
Forming the partition with a cut out provides an oil flow passage between
the bottom reservoir and the reduction gear chamber, so that the
lubricating oil in the bottom reservoir is easily drawn into the reduction
gear chamber.
Oil tray adapted to cooperate with the oil outflow passage ensures outflow
of oil splashed by the reduction gear unit. Forming the oil tray
integrally with a side wall of the transmission case enhances dissipation
of heat of the oil flowing out from the reduction gear chamber through the
transmission case and reduces the number of parts necessary to provide the
oil tray. Furthermore, positioning the oil tray off the vertical plane
including the center lines of rotation of the output shaft and the counter
shaft decreases the overall height of the transmission case. The oil tray
positioned off the vertical plane on the side remote from a housing wall
toward which the counter shaft and/or the reduction gear splashes oil
directly, so that the oil tray collects the oil splashes efficiently. The
oil splashes mostly flow down along the interior wall of the transmission
case and then are collected by the oil tray, so that the oil splashes are
effectively cooled during flowing down to the oil tray 26 along the
interior wall of the transmission case due to dissipation of heat through
the wall.
The transmission of the invention is further provided with a flow passage
of oil in the shafts at the input side of the gear assembly. This input
side oil flow passage comprises three divisional oil flow passages which
are formed in the reverse idler shaft, the input shaft and the counter
shaft, respectively and connected in series in this order. This oil flow
passage makes it possible that, even while a somewhat reduced amount of
oil is utilized, lubrication of moving parts associated with those shafts
is reliably and efficiently made.
As described above, with the output reduction gear type of transmission of
the invention, it is realized that, while lubrication of the transmission
gear and its associated parts is guaranteed, stir resistance of oil caused
due to rotations of the counter shaft and the counter gears is
significantly reduced with the result of suppression of an increase in oil
temperature and control of aggravation of the mechanical efficiency of
power transmission.
It is to be understood that the present invention may be embodied with
various changes, modifications and improvements, which may occur to those
skilled in the art, without departing from the spirit and scope of the
invention defined in the following claims.
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